Initial TreeView and Section Context

Major additions:

• TreeView of files containing section tag
• JumpTo..., runFile, runSection for .py file
• Added cache for most section related operation which improves performance

Others:

• General bug fixes and efficiency updates
• Deprecated usage of system clipboard for code sending to terminal
• Replaced usage of %load with %run -i and %run for all code section execution (single line execution continued using standard sendText)
• General update to README